• Journal of Korean Society of Water and Wastewater
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• v.30 no.1
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• pp.87-97
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• 2016

First of all, Fe or/and Mn immobilized granular activated carbons (Fe-GAC, Mn-GAC, (Fe, Mn)-GAC) were synthesized and tested to remove arsenate (As(V)). The results in batch test indicated that Fe-GAC removed As(V) effectively, even though the surface area of Fe-GAC was reduced largely. Moreover, adsorption isotherm test indicated that the experimental data fit well with Langmuir model and the maximum adsorption capacity ($q_{max}$) of Fe-GAC for As(V) was $3.49mg\;g^{-1}$, which was higher than GAC ($2.24mg\;g^{-1}$). In column test, the simulated water, which consisted of As(V), Fe(III), Mn(II) and Ca(II) in tap water, was used. Fe-GAC column with 1 hr of pre-washing time treated As(V) effectively while GAC column removed Fe(III) better than Fe-GAC column. Moreover, the increasing pre-washing time from 1 to 9 hour in Fe-GAC column enhanced Fe(III) removal with little negative impact of As(V) removal. Mostly, the column filled with Fe-GAC and GAC (i.e. the mass ratio of Fe-GAC:GAC = 2:8) showed the higher treatability of both As(V) and Fe(III), even it operated with 1 hr pre-washing time.

• Bulletin of the Korean Chemical Society
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• v.33 no.11
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• pp.3581-3588
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• 2012

A new series of acyclic mononuclear gadolinium(III) complexes have been prepared by Schiff-base condensation derived from 5-methylsalicylaldehyde, diethylenetriamine, tris(2-aminoethyl) amine, triethylenetetramine, N,N-bis(3-aminopropyl)ethylene diamine, N,N-bis(aminopropyl) piperazine, and gadolinium nitrate. All the complexes were characterized by elemental and spectral analyses. Electronic spectra of the complexes show azomethine (CH=N) within the range of 410-420 nm. The fluorescence efficiency of Gd(III) ion in the cavity was completely quenched by the higher chain length ligands. Electrochemical studies of the complexes show irreversible one electron reduction process around -2.15 to -1.60 V The reduction potential of gadolinium(III) complexes shifts towards anodic directions respectively upon increasing the chain length. The catalytic activity of the gadolinium(III) complexes on the hydrolysis of 4-nitrophenylphosphate was determined. All gadolinium(III) complexes were screened for antibacterial activity.

• Journal of the Korean Chemical Society
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• v.34 no.1
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• pp.51-62
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• 1990

Pentadentate Schiff base cobalt(II) complexes; Co(II)(Sal-DET) and Co(II)(Sal-DPT) were synthesized and these complexes were allowed to react with dry to form oxygen adducts of cobalt(II) complexes such as [Co(III)(Sal-DET)]$_2O_2$ and [Co(III)(DPT)]$_2O_2$ in aprotic solvents. These complexes have been identified by IR spectra, TGA, DSC, magnetic susceptibility measurements, and elemental analysis. It has been found that the oxygen adadduct complexes of $\mu$-peroxo type have hexaccordinated octahedral configuration with pentadentate schiff base cobalt(II) and oxygen, but the mole ratio of oxygen to cobalt(III) complexes of first step for oxygen adduct formation reaction of cobalt(II) complexes in aprotic solvents are 1:1. The redox reaction processes of Co(II)(Sal-DET), Co(II)(Sal-DPT), and oxygen adduct of cobalt(II) complexes were investigated by cyclic voltammetry and DPP method with glassy carbon electrode in 0.1M TEAP-DMSO and 0.1M TEAP-pyridine. As a result the reduction reaction processes of Co(III)/Co(II) and Co(II)/Co(I) for cobalt(II) complexes and oxygen adducts of cobalt(II) complexes are two irreversible steps of one eletron process, and reaction processes of oxygen for oxygen adducts complexes were quasireversible and redox range of potential was $E_{pc}$ = -0.97V∼-0.86V and $E_{pa}$ = -0.87V ∼ 0.64V.

• Journal of the Korean Vacuum Society
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• v.18 no.4
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• pp.245-253
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• 2009

For the growth optimization of InAs/GaSb (8/8-ML) strained-layer superlattice (SLS), the structure has been grown under various conditions and modes and characterized by the high-resolution x-ray diffraction (XRD) analysis. In this study, the strain modulation is induced by changing parameters and modes, such as the growth temperature, the ratio of V/III beam-equivalent-pressure (BEP), and the growth interruption (GI), and the strain variation is analyzed by measuring the angle separation of 0th-order satellite peak in XRD patterns. The XRD results reveal that the growth temperature and the V/III(Sb/Ga) ratio are major parameters to change the crystallineity and the strain modulation in SLS structures, respectively. We have observed that the SLS samples with compressive strain prepared in this study are show a transition to tensile strain with decreasing V/III(Sb/Ga) ratio, and the GI process is a sensitive factor giving rise to strain modulation. These results obtained in this study suggest that optimized growth temperature and V/III(Sb/Ga) ratio are $350^{\circ}C$ and 20, respectively, and the appropriate GI time is approximately 3 seconds just before InAs growth that the crystallineity is maximized and the strain relaxation is minimized.

• Journal of Korean Society of Environmental Engineers
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• v.27 no.6
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• pp.590-598
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• 2005

An adequate method to identify chromium separation, Cr(III) and Cr(VI), in water samples were studied by using High Performance Liquid Chromatography(HPLC) coupled with Inductively Coupled Plasma Mass Spectometer(ICP-MS) equipped with Dynamic Reaction Cell(DRC). The characteristic distribution of Cr(III) and Cr(VI) in the raw water taken at the six water intake stations in Seoul, was analyzed by the method developed by the authors. The chromium species separated by HPLC was isocratically conducted by using tetrabutylammonium phosphate monobasic(1.0 mM TBAP), ethylenediaminetetraacetic acid(0.6 mM EDTA) and 2% v/v methanol as the mobile phase. 5% v/v methanol was used as flushing solvent. A reactive ammonia($NH_3$) gas was used to eliminate the potential interference of $ArC^+$. Several Parameters such as solvent ratio, pH, flow rate and sample injection volume were optimized for the successful separation and reproducibility. Although it has been reported thai the separation sensitivity of Cr(III) is superior to that of Cr(VI), the authors observed Cr(VI) was more sensitive than Cr(III) when ammonia($NH_3$) gas was used as the reaction gas. It took less than 3 minutes to analyze chromium species with this method and the estimated detection limits were $0.061\;{\mu}g/L$ for Cr(III) and $0.052\;{\mu}g/L$, for Cr(VI). According to the results from the analysis on chromium species in the raw water of the six intake stations, the concentrations of Cr(III) ranged from 0.048 to $0.064\;{\mu}g/L$(ave. $0.054\;{\mu}g/L$) while that of Cr(VI) ranged from 0.014 to $0.023\;{\mu}g/L$(ave. $0.019\;{\mu}g/L$). Recovery ratio was very high($90.1{\sim}94.1%$). There were two or three times more Cr(III) than Cr(VI) in the raw water.

• Journal of the Korean Society of Tobacco Science
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• v.21 no.2
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• pp.160-170
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• 1999

Purification and biochemical experiments on the carboxylesterases-III (CE-III) from the indian meal moth, Plodia interpunctella (Hubner) were carried out to understand their enzymemological characteristics. The CE-III from the fifth instar larvae was purified by means of ammonium sulfate fractionation, gel permeation choromatography and ion exchange choromatography. The optimal temperature for the reaction of the CE-III on the 4 substrates ($\alpha$-Na, $\alpha$-Nb, $\beta$-Na and $\beta$-Nb) was confirmed at 4$0^{\circ}C$. The optimal pH for the reactions on the substrates $\alpha$-Na and $\alpha$-Nb was 7.5. But the optimal pH on the substrate $\beta$-Na and $\beta$-Nb was 8.0. The optimal substrate concentration for the reactions of the CE-III was 3.16 X 10$^{-3}$ M in $\alpha$-Na and $\beta$-Nb. On the substrate $\beta$-Na and $\alpha$-Nb, the optimal substrate concentration was 1.0 X 10$^{-3}$ M for CE-III. The $V_{max}$ and $K_{m}$ values of the carboxylesterases were varied by the substrates as followings: the $V_{max}$ of CE-III was 45.9 for $\alpha$-Na, 52.6 for $\beta$-Na, 36.4 for $\alpha$-Nb, and 83.3 ($\mu$ mol/min/mg protein) for $\beta$-Nb. The $K_{m}$ of CE-III was 1.43 X 10$^{-4}$ M for $\alpha$-Na, 3.57 x 10$^{-5}$ M for $\beta$-Na, 9.17 X 10$^{-5}$ M for $\alpha$-Nb, and 7.14 X 10$^{-5}$ M for $\beta$ -Nb, respectively. The CE-III seemed to have somewhat high thermostability considering that the temperature for effective denaturation on activity was about 5$0^{\circ}C$ ～ 6$0^{\circ}C$.EX>.EX>.

• Resources Recycling
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• v.31 no.1
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• pp.12-20
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• 2022

The smelting reduction of spent lithium-ion batteries results in metallic alloys containing Co, Cu, Fe, Mn, Ni, and Si. A process to separate metal ions from the sulfuric acid leaching solution of these metallic alloys has been reported. In this process, ionic liquids are employed to separate Fe(III) and Cu(II). In this study, D2EHPA and Cyanex 301 were employed to replace these ionic liquids. Fe(III) and Cu(II) from the sulfate solution were sequentially extracted using 0.5 M D2EHPA with three stages of cross-current and 0.3 M Cyanex 301. The stripping of Fe(III) and Cu(II) from the loaded phases was performed using 50% (v/v) and 60% (v/v) aqua regia solutions, respectively. The mass balance results from this process indicated that the recovery and purity percentages of the metals were greater than 99%.

• Journal of the Korean Society of Food Science and Nutrition
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• v.43 no.6
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• pp.842-853
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• 2014

For developing indigestible lipids, symmetric triacylglycerol (ST) and asymmetric triacylglycerol (AT) were produced by enzymatic interesterification using high oleic sunflower oil, palmitic ethyl ester, and stearic ethyl ester in a shaking water bath. Used enzymes were Lipozyme RMIM for ST and Lipozyme TLIM for AT. To remove ethyl ester from reactants, methanol fractionation (reactant : methanol=1:5, w/v, $25^{\circ}C$) and florisil separation (reactant : florisil=1:8, w/w) were applied. Acetone fractionation (reactant : acetone=1:9, w/v) was implemented to separate triacylglcerol (TAG) species into ST and AT. Fractions I (before fractionation), II (after fractionation, liquid phase) and III (after fractionation, solid phase) were separated from ST, whereas fractions IV (after 1st fractionation, liquid phase) and V (after 2nd fractionation, solid phase) were from AT. From sn-2 fatty acid composition analysis, the sum of palmitic acid (C16:0) and stearic acid (C18:0) was 4.9~6.5 area% in ST (I, II, III), and 41.9~43.9 area% in AT (IV, V). In vitro digestion was performed for 0, 15, 30, 60, and 120 minutes at $37^{\circ}C$ in a shaking water bath. For the digestion results, hydrolysis of V was only 40% compared to others (I, II, III, IV) at 120 minutes due to its melting point ($49^{\circ}C$). However, initially (15 minutes), hydrolysis (%) was as follows: V$32.5^{\circ}C$, $31.8^{\circ}C$) and different slip melting points ($31.3^{\circ}C$, $19.5^{\circ}C$). Even though IV has a lower TAG content composed of two saturated fatty acids than III, it had a similar melting point.

• Resources Recycling
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• v.26 no.4
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• pp.34-41
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• 2017

The effect of Mn(II) concentration on the anodic reactions occurring on a Pb-Ag electrode in sulfuric acid solutions has been studied by potentiostatic oxidation in the potential range of 1.8 to 2.0 V. High oxidation potentials and low initial concentrations of Mn(II) resulted in higher concentrations of soluble Mn(III) ions which were obtained from spectrophotometric analysis of the solution after oxidation. $MnO_2$ was deposited on the electrode by electrochemical oxidation of Mn(II) at 1.8 and 1.9 V, while it was formed by disproportionation of Mn(III) at 2.0 V. No $PbO_2$ was formed in the presence of Mn(II) during potentiostatic oxidation treatment for two hours at 1.8 V. Chemical reduction of $PbO_2$ with Mn(II) led to a decrease in the amount of $PbO_2$ as Mn(II) concentration increased at 1.9 and 2.0 V.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09a
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• pp.38-38
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• 2006